Washington: Pakistan should "cut-off" ties with Taliban, the US has said pointing out that it has "long standing concerns" over ISI's links with the Afghan insurgent groups.

Pentagon spokesperson Navy Capt John Kirby told reporters during an off-camera briefing that the facts laid bare by the damning NATO report, which blew the lid off ISI's "manipulation" of Taliban's senior leadership, were "not a new notion" and these concerns have been raised earlier as well.

"This is not a new notion, we made those concerns clear and the Secretary has been very clear about the ongoing problem of safe havens inside Pakistan for these groups," Kirby said on Wednesday referring to a new NATO report on Taliban which says that the ISI continues to help the extremist group, which wants to come back to power in Afghanistan.

"We have made it clear already that Pakistan needs to act against safe heavens. We would like ties between some elements of ISI and Taliban to be cut-off," he said.

Kirk said the US had "longstanding concerns" about the ties between the elements of the ISI and the Taliban but did not give details on what elements of the ISI he was referring to.

Without going into the specific of the classified report, Kirby said the US does have information that the Taliban is becoming splintered and is not a monolithic organisation.

For instance, he said, a couple of weeks ago about 50 Taliban came in and asked to be reintegrated. The reason they gave was that they can't sleep at one place for more than a day and that they do not want to kill their own Afghan countrymen, he said.